PURPOSE: To enable to use a scale for multiple purposes, by a method wherein a polygonal scale for indicating printing digit places is provided on the lower side of a printing head.

CONSTITUTION: On the lower side of the printing head 1 opposed to a platen 2 provided in a main body of a printer, the polygonal scale 8 provided with graduations conforming to plural kinds of printing digit places on lateral surfaces thereof is provided in parallel with the platen 2 so that an oblique side of the scale 8 guides a paper 9 into a guide hole 7. Accordingly, the printing digit places can be indicated regardless of whether the printing paper is a continuous paper or a slip form paper.